When the 3PP creator produced his product, a contract was formed between WotC and the 3PP. WotC can't unilaterally change the contract. The terms are set when both sides have agreed to the contract and performed what they need to perform. Deauthorizing 1.0a later applies to future products, not the ones already produced. If I were to use the Runeblades supplement's OGC for something I want to create, I would need to follow the terms of OGL 1.0a, which includes putting a copy of that license in my product.
Ok, and so this sounds different than what I thought you were saying above.
It didn't sound like you were.arguing that 1.0a effectively continued post "deauthorization" (assuming WotC could).
It sounded like you were saying publishers could come up with some new verbiage and continue on developing the chain of 1.0a content without putting the 1.0a license in and doing everything it said